The present application generally relates to power circuits. More particularly, the present application relates to a power converter.
Power converters are utilized on a multitude of applications where power conversion is required, such as, in power supply applications. One such application includes supplying power to electronic equipment on-board an aircraft. Aircraft power supplies can be used to supply power to a variety of equipment, including but not limited to radios, computers, navigation equipment, flight controls, radar, sensors, etc.
Conventional aircraft power supplies operating at high power levels generally receive three phase alternating current (AC) input power and use line frequency transformers. This approach is a heavy and bulky generally not desirable for aircraft applications.
Generally, conventional aircraft three phase power supplies have relied on passive techniques to meet power factor and harmonic current requirements. One such passive technique often uses a polyphase transformer coupled to a rectifier array. In addition, components associated with such a design can be expensive.
Another conventional power supply approach has utilized a power factor correction circuit to meet stringent power factor and harmonic current requirements for alternating current (AC) loads. This conventional approach uses a boost power factor control circuit followed by a second converter to provide an isolated output. The topology for this circuit has several drawbacks including reduced efficiency, reliability, high in-rush current, and high parts count.
Usage of the Single-Ended Primary Inductance Converters (SEPIC) operating in continuous conduction mode have not been widely utilized in power factor correction applications due to poor performance caused by power stage circuit resonance. The degraded performance is due to the need to limit bandwidth to avoid control loop instability caused by resonance between the coupling capacitor and circuit inductance. Avionics power systems use higher line frequencies (360-800 Hz) and require high bandwidth in power factor corrected converters. The performance degradation caused by the circuit resonance can be improved with an active clamp. Active clamps can also increase efficiency using a soft switching technique, however the active clamp can add significant complexity and can be difficult to implement reliably due to high voltages in the primary circuit.
The SEPIC topology does offer the attractive potential to achieve isolation in one converter stage. This isolation allows three converters to combine output power in a three phase configuration. Previous attempts to implement individual converters operating from each phase combined into one single output often interact in an undesirable manner. This interaction is caused by the need for one common error amplifier to regulate the output voltage and also provides precise control of power sharing between the individual converters.
Therefore, there is a need for a power converter which closely shares individual phase line circuits to reduce power systems phase load imbalance. Further, there is a need for an aircraft three phase input power supply that utilizes active power factor correction. Further still, there is a need for an aircraft power supply that is lighter and less expensive and meets stringent aircraft harmonic performance and power factor performance requirements. Yet further still, there is a need for a power supply that actively cancels sources of imbalance and prevents feedback loop interaction between converters.